gunboat

gunboat, small warship for use on rivers and along coasts in places inaccessible to vessels of larger displacement. In the U.S. Civil War both sides used as gunboats, on the Mississippi and other rivers, any boat that had an engine and had room to mount a gun. Gunboats were widely employed by the European powers in the Far and Middle East and Africa during the late 19th and early 20th cent. for police duty. More recently, gunboats equipped with gas-turbine propulsion plants were used by the U.S. navy for coastal patrol operations during the Vietnam War.